Stormwater runoff is rain that falls on streets, parking areas, sports fields, gravel lots, rooftops or other developed land and flows directly into nearby lakes, rivers and other water landforms. The drizzling or pounding rain picks up and mixes with contaminants on the ground, such as oil, grease, metals and coolants from vehicles; fertilizers, pesticides and other chemicals from gardens and homes; bacteria from pet wastes and failing septic systems; soil from construction sites and other bare ground; soaps from car or equipment washing; and accidental spills, leaky storage containers, and whatever else ends up on the ground. The polluted runoff then rushes into nearby gutters and storm drains and into streams, lakes, rivers, and bays. In most areas, stormwater runoff enters these receiving water bodies without being cleaned of pollutants.
Increasingly, government entities are instituting strict regulations for the management of stormwater and industrial runoff. Despite increasing public concern surrounding this issue, the current infrastructure does not adequately control the release of contaminated stormwater or combined sanitary sewage and stormwater to receiving water bodies. Stormwater and industrial runoff can be contaminated with a highly variable mix of particulate-bound and dissolved contaminants. Due to the large volume of water discharged into water bodies during runoff events, even small quantities of contaminants can have a significant environmental impact.
It is desirable to be able to collect combined sewer and stormwater effluent samples for laboratory analysis to facilitate an accurate characterization of contaminants in water discharged into bodies of water. These contaminants are typically bound to particulates and, to a lesser degree, in the dissolved phase. Quantitation limits associated with the particulate-phase of the effluent are particularly challenging to achieve, in that the low target quantitation limits require a sufficiently large mass of solids to be collected for detection via standard, approved laboratory analytical methods. To obtain the required mass of solids, it is essential that a sufficient volume of effluent be collected in the field.
To determine contaminant load in water, it is necessary to analyze, separately, the dissolved and solids matrices (or fractions). Traditionally, the solids fraction is obtained by forcing water through a filter, whereby trapped solids are sent to a laboratory for chemical analysis. To ensure that all of the trapped solids are accounted for in the analysis, the whole filter is processed (i.e., it would be impossible to volumetrically separate the trapped solids from the filter). Consequently, the filter must not have any trace contaminants present as artifacts that can contribute to the analytical results obtained (which would produce a biased result). This process has several additional limitations, including the ability to only trap small masses of particulates, which precludes detection of many chemicals at trace concentrations, and which necessarily requires many filters, possibly hundreds when multiple analyses are necessary to characterize the range of contaminants of interest. This methodology further suffers from a lack of efficiency and poor quality control due to the many potential sources of error or contamination, including the moisture retained in the filters that adversely affects the analytical method.
U.S. Pat. No. 4,252,020 to Ongley describes a method and apparatus for the quantitative recovery of solids suspended in a fluid involving the use of a continuous flow centrifugation sampling apparatus. Although this system represents an improvement over the filter processing method above, it does not provide a sufficient “clean room” environment to facilitate accurate trace contaminant detection, nor does it have a sufficiently high processing capacity. Consequently, accuracy and trace contaminant detection is reduced.
In view of the above-described problems and limitations, there is a need for improved sample collection systems for water quality monitoring. The present invention overcomes the above-described problems and limitations by providing an efficient, high capacity, high throughput sample collection system in a clean room environment so as to provide increased accuracy, sensitivity and characterization of contaminants in large volume water sampling investigations.